Abstract：In order to solve the defects of high energy consumption, high breakage rate and poor stability of the dilute phase pneumatic conveying of grain particles. Numerical simulation was conducted on the dense phase fluid transport of grain in the horizontal tube by using Euler double fluid and k-εmodel on the platform of computational fluid dynamics software FLUENT. The influence of turbulence was found when the material flows in the gas-solid two-phase flow by comparing the simulation results with the experimental results. The change rule of performance parameters such as particle concentration distribution, velocity of conveying gas and pressure loss in pipeline due to the use of variable diameter pipe were analyzed.The flow characteristics of dense phase pneumatic conveying were discussed. It is concluded that the loss of air velocity and pressure will decrease by 15% and 20% respectively with the increase of the length of the variable diameter.

Keywords： dense phase pneumatic conveying; gas-solid two-phase flow; horizontal stepped pipeline; grain particles; numerical simulation